Modern aircraft are equipped with a generous assortment of sensors and instrumentation to facilitate operation of the aircraft. Nearly every parameter critical to safe and efficient operation is accurately monitored in real time, with one notable exception. The gross weight and longitudinal center of gravity, both critical to safe and efficient operation, are based on a variety of inputs, which include a mixture of predetermined “known” values, measured values, and estimates based on statistical sampling. The Load and Trim Sheet, or Manifest, is the outcome of the load planning process that utilizes these inputs. Although the load planning process is highly controlled, there are opportunities for undetected errors. In addition, even if the load plan is perfect, the actual loading process can introduce errors that cannot be detected without a real-time measurement of the “as loaded condition” of the aircraft. And, during the loading process the aft section can become disproportionately heavy (due to early aft loading of cargo and/or baggage) resulting in the aircraft tipping (tail down), which can cause damage to the fuselage.
According to the National Aerospace Laboratory Report Number NLR-TP-2007-153, the majority (more than 90%) of weight and balance problems identified could be eliminated if there was a system available to the flight crew that would do an automatic onboard weight and balance assessment.
Present on-board aircraft weight and balance systems (WBS) require a multitude of precision sensors (usually one or more per wheel location) historically resulting in a system that is too expensive to be practical for smaller, lower cost aircraft. Therefore, only the very high value large wide body aircraft currently utilize these systems.
An analysis of aircraft loading parameters and in-service data has shown that the most critical, and also the most challenging, loading parameter is the loading of the aircraft within the center of gravity limits. The operator can usually determine the gross weight of the aircraft within an acceptable degree of accuracy, and aircraft performance is reasonably tolerant of minor gross weight uncertainty—as long as the center of gravity is within limits. However, if the center of gravity is outside of the acceptable envelop, by even a few inches, the aircraft can become uncontrollable and unsafe. Therefore, a lower cost solution need not focus on highly accurate gross weight determination, but must instead be optimized for an accurate real time measurement of the actual center of gravity.